1. Technical Field
The present invention relates to a signal processing apparatus.
2. Related Art
Recently, as the resolution of a solid-state imaging element such as a charge coupled device (CCD) image sensor and a complementary metal oxide semiconductor (CMOS) image sensor becomes higher, a demand for an information device having an imaging function such as a digital still camera, a digital video camera, a cellular phone, and a personal digital assistant (PDA) is rapidly increasing. Meanwhile, the information device having an imaging function as described above is referred to as an imaging device.
However, a focus control method which focuses on a main subject includes a contrast auto focus (AF) method and a phase difference AF method. Since the phase difference AF method may detect a focusing position with high precision at a high speed as compared with the contrast AF method, the phase difference AF method is widely employed in various imaging devices.
As a solid-state imaging element mounted in an imaging device which controls a focus by a phase difference AF method, for example, a solid-state imaging element in which a pair of focus detecting pixel cells having light shielding film openings, which are off-centered in reverse directions to each other, are discretely provided on an entire surface of an imaging region is used (see Patent Literature 1 (JP-A-2010-62640)).
An area of the light shielding film opening of the focus detecting pixel cell is smaller than those of the other normal pixel cells and as a result, it is insufficient to use the output signal of the focus detecting pixel cell as a captured image signal. Therefore, it is required to correct the output signal of the focus detecting pixel cell.
Patent Literature 1 discloses a method that selectively performs first correction processing which interpolates an output signal of a focus detecting pixel cell using output signals of normal pixel cells around the focus detecting pixel cell and second correction processing which amplifies and corrects the output signal of the focus detecting pixel cell in accordance with a variation of the output signals of the normal pixel cells around the focus detecting pixel cell.